I messed around with a bunch of methods to achieve background music playing in the terminal and nothing seemed to work on my machine. My only thought now is doing all these operations in python (import youtube-dl as a library, slicing up the audio using some other library and then playing it) and forking that python script to the background.

I have no idea if this works as a git hook, but this runs in a few milliseconds for me and returns to my shell with the audio playing in the background. I can even kill the shell that ran the python process.